--  @testpoint:opengauss关键字preorder(非保留)，作为函数名

--关键字不带引号-成功
drop function if exists preorder;
create function preorder(i integer)
returns integer
as $$
begin
    return i+1;
end;
$$ language plpgsql;
/
drop function preorder;
--关键字带双引号-成功
drop function if exists "preorder";
create function "preorder"(i integer)
returns integer
as $$
begin
    return i+1;
end;
$$ language plpgsql;
/
drop function "preorder";
--关键字带单引号-合理报错
drop function if exists 'preorder';
create function 'preorder'(i integer)
returns integer
as $$
begin
    return i+1;
end;
$$ language plpgsql;
/
--关键字带反引号-合理报错
drop function if exists `preorder`;
create function `preorder`(i integer)
returns integer
as $$
begin
    return i+1;
end;
$$ language plpgsql;
/